1. Field of the Invention
This invention relates to organosol flocculants, which in an organic phase contain a very finely-distributed water-soluble polymer or a polymer dissolved in water which is composed primarily of acrylic and/or methacrylic monomers.
2. Discussion of the Background
Water-in-oil emulsions of, for instance, high molecular weight polyacrylamides or acrylamide copolymers have achieved particular importance in technical applications as liquid products which have a high percentage of solids while still retaining manageable viscosity. The reversability of the emulsion makes rapid production of aqueous solutions possible. They are also used, particularly as flocculants, in the refining of drinking water, for instance, or in purifying public and industrial effluents.
There are well known procedures for manufacturing water-in-oil emulsions of compounds of high molecular weight by polymerization of water-dissolved, ethylene-unsaturated monomers in an oil-phase. Oils used in the production of polymer water-in-oil emulsions are liquid, non water-soluble, organic substances or mixtures of these substances. Thus, according to DE-A 1 081 228, the oil phase may consist of any inert hydrophobic liquid which may include hydrocarbons and chlorinated hydrocarbons, for example, toluol, xylene, o-dichlorobenzene and propylene dichloride.
According to DE-B 21 54 081, oils from a large group of organic liquids can be used, for instance, liquid hydrocarbons and substituted liquid hydrocarbons, including both aromatic and aliphatic compounds. Benzol, xylol, mineral oils, kerosine, naphthas and an isoparaffin-based oil, which is particularly well-suited, are named as examples of such liquid hydrocarbons. DE-A 22 26 143 also lists the above-mentioned organic substances to create the oil phase and DE-B 24 32 699 again indicates aromatic hydrocarbons and aliphatic hydrocarbons, such as paraffin oils and tetrachloroethylene, for a hydrophobic organic dispersion medium.
DE-A 33 02 069 describes preparations which, among other things, are used as flocculants in which the oil phase may consist exclusively of the above-named aromatic and aliphatic hydrocarbons of natural plant or animal triglycerides, such as olive oil, peanut oil, cotton oil, coconut butter, beet oil, sunflower oil, and of fatty acid monoesters, primarily C.sub.1-4 alkyl esters of C.sub.12-24 fatty acids such as oleic, palmitic, or hexadecylic acid. Mixtures of the above may be used if necessary.
EP-A 45 720 and EP-A 80 976 describe water-in-oil emulsion polymers for cosmetic applications which require hydrophobic organic liquids such as aliphatic or aromatic hydrocarbons, animal or vegetable oils and the corresponding denatured oils as polymers in the oil phase.
The use of organic flocculants as the base of water-in-oil emulsions with an oil phase of aliphatic and/or aromatic hydrocarbons, in waste-treatment installations, for example, carries with it the growing danger of contaminating the ground water and, consequently, the supply of drinking water because of the oil residue in the sludge that is deposited.
The explanation for this lies in the fact that the treatment of sewage in a large city, for instance, causes several hundred kilograms of oil to be deposited with sewage sludge and that the decomposition of aliphatic and aromatic hydrocarbons by micro-organisms is only possible in the presence of oxygen and relatively slow even then.
To remove the danger of poisoning the soil with such hard-to-degrade oils, the sludge is now burned. Another possibility would be to use polymer water-in-oil emulsions in which the oil phase consisted of substances which are more readily bio-degradable as, for instance, in the above-mentioned DE-A 33 02 069. However, burning the oil in the sludge or using natural plant or animal oils and C.sub.12-24 fatty-acid monoesters in the oil phase increases the cost of flocculants in the sewage-treatment installation considerably. Aside from the cost of natural oil, which is several times that of mineral oils, the natural products are less uniform and fluctuate in their composition which has an unfavorable effect on the quality of the organosol and its use as a flocculant.
A need continues to exist for polymer water-in-oil emulsions in which the continuous oil phase consists of substances which are more readily bio-degradable than the previously used hydrocarbon oils and which, compared to natural oils and fats, can be produced more economically and which have more consistent properties.